Additional issues that need to be addressed include:
Is the cost of a sediment transport analysis commensurate with the cost of the bridge and
the accuracy of the analysis?
Are there sediment transport data available from the USGS or other Federal or state
Agencies for this stream or similar streams?
4.11.2 Step 2: Determine Scope of Sediment Transport Analysis
Determine if the need for information on the quantity of sediment being transported is for the
quantity transported by the occasional high or peak flows or for the amount transported
annually, i.e., determine the sediment transport design parameters.
To check previous scour calculations, only sediment transported by high or peak flows
may be needed.
The design of a check dam or debris basin may require annual or multi-year cumulative
quantities of sediment transport.
Refining estimates of long-term aggradation or degradation will require multi-year
cumulative quantities.
4.11.3 Step 3: Determine the Type of Analysis
The types of analyses available to determine the quantity and gradation of sediment
transport are field measurements, computer models, and basic methods given in this
chapter.
Field Measurement
Field measurement to determine sediment transport is a specialized activity and generally
should be contracted for. The USGS and the U.S. Army Corps of Engineers are specialists
in this type of field measurement. Field measurements used in conjunction with the modified
Einstein method (Colby and Hubbell 1962, Vanoni 1977, Simons and Senturk 1992) provide
the most accurate method of determining the total sediment discharge of a stream.
Basic Methods for Sediment Transport Calculations
The methods and equations given in this chapter will normally be sufficient for most
determinations of the bed-material transport for a given discharge or to develop a bed-
material discharge rating curve to be used with a flow duration curve to determine the annual
sediment discharge. Only for the most important and costly bridges would it be necessary to
use field measurements and/or computer models to determine bed-material transport.
The basic equations and methods given in this chapter and recommended for practical
applications are:
Meyer-Peter and Mller (1948) bed load equation (also USBR 1960)
Colby's (1964) curves and method
4.35
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